   Chat room list component has a subscription dependency on `:chat-rooms` which will
   return the list of chat rooms to render.
 
-  Usually you would either pass the chat rooms subscription from layout to sidebar to the
+  Usually, you would either pass the chat rooms subscription from layout to sidebar to the
   chat room list component, or the chat room list component would have a dependency
   on a global `:chat-rooms` subscription.
 

  "Creates a component system.

  Component system is a group of components that are interdependent. Each component
  system must define a `:main` component which will be returned from the `system`
  function.

  `system` function resolves dependencies between components.

  - `:renderer` - A renderer function (Reagent component)

  The UIComponent record is a way to list all the dependencies for a component. When
  the application is started each component's renderer function will be partially 
  applied with a version of its UIComponent that has the component and subscription
  dependencies resolved.

  This allows you to write components that are completely decoupled from the rest
